Gas blast circuit interrupter using main movable contact as blast valve

ABSTRACT

A high-speed gas blast circuit breaker in which SF6 is used as the mechanical drive for the movable contact and as the dielectric medium for maintaining a high dielectric between the open contacts and for extinguishing arcs. Two or three movable elements are used; an annular movable contact and a cutoff valve and, in some cases, a follower contact. The two elements may be incorporated into one movable body. Each of the movable elements have radially extending surfaces defining pistons so that they may be moved by control air pressure. The movable contact serves as an annular seal in a barrier which separates a high-pressure region from a low-pressure region when the contact is closed. The movable contact acts in the manner of a cork so that, when the seal is broken, the contact is accelerated toward its open position, and fluid from the high-pressure side flows through the annular gap formed and through the arc in its passage to the lowpressure side. The apparatus is mounted in a suitable switch gear enclosure.

United States Patent [72] lnventors William A. Carter Devon, Pa.; llansruedi Aumayer, Suhr, Switzerland [21] Appl. No. 823,116 [22] Filed May 8, 1969 [45] Patented Oct. 12, 1971 [73] Assignee l-T-E Imperial Corporation Philadelphia, Pa.

[54] GAS BLAST CIRCUIT INTERRUPTER USING MAIN MOVABLE CONTACT AS BLAST VALVE 3 Claims, 16 Drawing Figs.

[52} US. Cl 200/148 R, 200/148 B, 200/148 BU [51] Int. Cl Il0lh 33/86, 110111 33/70 [50] Field of Search 200/148 R, 148 B, 148 E, 148 BU [56] References Cited UNITED STATES PATENTS 3,099,733 7/1963 Ridings 200/148 B X 2,972,666 2/1961 Forwald ZOO/148.2 3,118,996 1/1964 Forwald ZOO/148.2 FOREIGN PATENTS 1,534,616 6/1968 France 200/148 1,161,620 1/1964 Germany 1,229,164 11/1966 Germany.... 200/148 1,271,241 6/1968 Germany 200/148 6,505,408 10/1966 Netherlands 200/148 Primary Examinerl*l. 0. Jones Assistant Examiner-Robert A. Vanderhye Attorney0strolenk, Faber, Gerb & Soffen and a cutoff valve and, in some cases, a follower contact. The

two elements may be incorporated into one movable body. Each of the movable elements have radially extending surfaces defining pistons so that they may be moved by control air pressure. The movable contact serves as an annular seal in a barrier which separates a high-pressure region from a lowpressure region when the contact is closed. The movable contact acts in the manner of a cork so that, when the seal is broken, the contact is accelerated toward its open position, and fluid from the high-pressure side flows through the annular gap formed and through the arc in its passage to the lowpressure side. The apparatus is mounted in a suitable switch gear enclosure.

PATENTEDum 12 197i SHEET 0101' 10 N M I LMI N PATENTEDnm 12mm I 3,612,799

SHEET UEUF 10 PAIENTEnnm 12 19?: 3,612,799

- SHEET O30F 10 PATENTEDUCT 12 I971 SHEET CBUF 1O PAIENTEunm 12 I97l 3612.7 99

sum 07 0F 10 PATENTEDum 12 I97! SHEET C8UF 1O QYMIMN PATENTEDBBT 2 IHY SHEET as 0F 10 3,612,799

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SHEET 10 0F 10 PAIENTED [JCT 12 l97l GAS BLAST CIRCUIT INTERRUPTER USING MAIN MOVABLE CONTACT AS BLAST VALVE RELATED APPLICATIONS This application is related to application Ser. No. 823,115, filed May 8, 1969, in the name of Otto Jensen, entitled Gas Blast Circuit Interrupter Using Main Movable Contact As Blast Valve, and assigned to the assignee of the present invention.

This invention relates to gas blast circuit interrupters and more particularly relates to a gas blast interrupter having two or three movable elements which are immersed in, and moved by, SF

Gas blast circuit interrupters are well known, which use SF, as a high-dielectric fluid. It has been difficult to use SF as the medium for driving movable parts in the past because SF is too heavy to respond rapidly to pressure change. Consequently, it is customary to use spring biases, or air as the drive means for the contact. The present invention provides a novel structure which permits the use of SF as the driving medium for the contact of a gas blast interrupter wherein the contact serves as a cork in a barrier separating the highand low-pressure regions of a tank which encloses the circuit inter- .rupter equipment. This novel configuration permits highspeed operation whereby the circuit is interrupted in about 33 milliseconds from the time of the trip signal. Moreover, the equipment will take up about one-fourth the volume of an equivalent air blast interrupter.

As a further advantage of the invention, the open contacts are immersed in the high-pressure side of the interrupter, whereas prior art devices usually have their open contacts immersed in the low-pressure side of the unit. Thus, smaller contact openings are needed. Moreover, with the present novel construction, the gas system is completely closed, with no SF being lost to the external atmosphere during operation. The mechanical simplicity of the unit having, at most, three moving parts permits the hermetic sealing of the unit and virtually no maintenance.

Accordingly, a primary object of this invention is to provide a novel gas blast circuit breaker having a minimum number of moving parts.

Another object of this invention is to provide a novel circuit breaker using SF, as the means to drive the movable contact which can interrupt circuits within 33 milliseconds.

A further object of this invention is to provide a novel gas circuit breaker which can be hermetically sealed.

Another object of this invention is to provide a novel SF breaker in which a movable cylindrical contact serves as a cork between a high-pressure and low-pressure region.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings in which:

FIG. 1 is a side view of the interrupter of the invention with the tank partly broken away.

FIG. 2 is an exploded perspective view of the stationary contact assembly of FIGS. 1, and 6.

FIG. 3 is an exploded perspective view of the movable contact assembly of FIGS. 1, 5 and 6.

FIG. 4 is an exploded perspective view of the tank assembly of FIG. 1.

FIG. 5 is a cross-sectional view of the circuit interrupter of FIGS. 1 to 4 with the movable contact closed.

FIG. 6 is a partial view of FIG. 5 with the movable contact open.

FIG. 6a shows a plan view, partly in section, of a typical cluster contact of FIGS. 5 and 6.

FIG. 7 shows a cross-sectional view of a second embodiment of the invention with the interrupter shown closed above the centerline of the movable contact and open below this ccnterline.

FIG. 8 is a cross-sectional view of FIG. 7 taken across section lines 8-8 in FIG. 7.

FIG. 9 is a cross-sectional view of a modified stationary contact structure.

FIG. 10 is a cross-sectional view similar to FIG. 7 showing a further embodiment of the invention.

FIG. 11 is a cross-sectional view similar to FIG. 7 showing a still further embodiment of the invention.

FIG. 12 is a cross-sectional view of FIG. ll taken across section line l2 12 in FIG. 11.

FIG. 13 is a top schematic view of the circuit breaker compartment and bus compartment of switch gear receiving three interrupters which form a multiphase circuit breaker.

FIG. 14 is a front plan view of the switch gear of FIG. 13 with the front wall removed to show the interior of the switch gear.

FIG. I5 is a side plan view of FIG. 13 with the sidewall removed to show the interior of the switch gear.

Referring first to FIGS. 1 to 6, there is shown a circuit interrupter having a rating of 3,000 amperes at a voltage of 38 kv. at 1,500 MVA when used in a three-phase arrangement. One pole of the unit is shown, having a housing 40 (FIGS. 1 and 4) which consists of insulation cylinders 41 and 42 (FIGS. 1, 4 and 5) which have end cups 43 and 44, respectively, suitably secured thereto. Each of cylinders 41 and 42 have pressure connection fittings 45 and 46, respectively, and suitable lifting hooks 47 and 48, respectively (FIGS. 1 and 4).

Each of cylinders 41 and 42 have bus receiving tubes 49 and 50 extending therefrom and fixed to cylinders 41 and 42. Each of tubes 49 and 50 have flanges 53 and 54 (FIGS. 4 and 5) which have suitable bolt openings. Two tubular buses 55 and 56 (FIGS. 1, 2, 3 and 5 which have insulation coatings 57 and 58, respectively, are then secured to tubes 49 and 50 by flanges 59 and 60, respectively, which are bolted to flanges 53 and 54, respectively (FIGS. 1 and 5). Note that suitable gaskets 59a and 60a are provided between flanges 53-57 and 5458, respectively. Each of buses 55 and 56 are terminated with contacts, to be described later, which are connected to the circuit to be protected by suitable disconnect contacts.

Bus 55 then carries the stationary contact assembly 61, shown in FIGS. 1, 2 and 5, where the bus 55 has a conductive end plate 62 which receives a bolt 63 which is threaded into lower plate portion 65 of stationary contact housing 64 (FIGS. 2 and 5). Stationary contact housing 64 consists of lower plate portion 65 which is welded to a hollow conductive cylinder 66 which has an end flange 67. A stationary contact body 68 is inserted within cylinder 66 and bolted to the end thereof, as shown by bolts 69 and 70 in FIG. 5. The right-hand end of contact body 68 carries an arcing tip 71.

Semistationary contact cylinder 72 is disposed within the annular space between cylinder 66 and body 68 and is biased to the right in FIGS. 5 and 6 by biasing spring 73. Contact between semistationary contact 72 and contact body 68 is obtained by contact cluster 74 which is clamped to flange 67 by cup-shaped clamping plate 75. Clamping plate 75 has a central opening therein which has a chamfered surface which serves as a valve seat, as will be described later. Contact cluster 74 is of the well-known variety of individual contact segments which individually are biased away from one another by springs between the individual contact segments.

FIG. 6a shows a typical contact cluster which can be used for cluster 74 in partial cross section. Thus, a plurality of contact segments such as segments 74a, 74b and 74c are biased away from one another by springs such as springs 74d and 74e captured between adjacent segments.

The movable contact and valve structure are supported, in part, from bus 56, as shown in FIGS. 3 and 5. Thus, bus 56 has a conductive end plate which passes bolt 81 which is threaded into flat base portion 82 (FIG. 3) of conductive cylinder 83. Conductive cylinder 83 receives control valve apparatus which will be described later. The left-hand surface of cylinder 83 is bolted to the flange of cylinder 85 which also locks against an annular shoulder of insulation ring 86 (FIGS. 1, 4 and 5) which also supports the movable contact assembly and provides a gas barrier to divide the interior of housing 40 into a low-pressure region and a high-pressure region, as will be described later. Insulation ring 86 has a raised outer shoulder 87 which is received between two rings 88 and 89 which are secured to the opposing ends of cylinders 41 and 42. Sealing rings 90 and 91 (FIG. insure a pressuretight joint.

A cupshaped contact holder 92 is clamped against the lefthand end of cylinder 85 by bolts such as bolts 93 and 94 (FIGS. 3 and 5) which thread into tapped openings in the lefthand end of cylinder 85 with contact holder 92 receiving contact cluster 95 (which is identical to contact cluster 74 of FIG. 2). A clamping plate 96 holds contact cluster 95 in cup 92.

The main movable contact cylinder 97 is then mounted to slide within the cylinder defined by the inner diameter of cylinder 85, and the inner diameters of members 92, 95 and 96 with electrical contact to cylinder 83 and bus 56 made by contact cluster 95. The movable contact has an annular arcing tip 98 and a sealing ring 99. Arcing tip 98 engages a corresponding arcing ring of semistationary contact 72 when the breaker is closed, as shown above the centerline in FIG. 5, with the outer cylindrical portion of contact 97 engaging cluster 74. When the breaker is closed, sealing ring 99 engages the interior diameter bias cut of plate 75 to define a pressure seal between the rightand left-hand sides of the interior of housing 40. Suitable sealing rings are provided between the sliding surfaces receiving contact 97 to prevent pressure leakage.

The interior diameter of contact 97 rides on an interior gas blast directing nozzle and guide consisting of nozzle section 100 and 101. Section100 is secured to cylinder 85 by suitable bolts and carries a shock-absorbing ring 102 which absorbs the opening force of contact 97 Section 101 is secured along the inner diameter of cylinder 83 by suitable bolts extending through the flange on the right-hand end of cylinder 83.

A sliding cutoff valve 103 then slides on the outer diameter of section 103 and the right-hand end of valve 103 cooperates with annularseal 104 in valve body 105. Valve body 105 is connected to spider plate 106 by bolt 107 with the flange 108 of spider plate 106 connected to cylinder 83. A valve guide plate 109 is captured between cylinder 83 and plate 106. A second flange 110 of plate 106 is connected to flange 111 of arc cooler tube 112. I

As shown in FIG. 5, a ball and detent mechanism 112 is provided to delay movement of valve cylinder 103 to its closed position, shown in FIG. 6. Valve body 105 also receives the arcing contact rod 113, which has an arcing tip 114 adjacent the arcing tip of contact 71.

A suitable compressor, not shown, is connected between fittings 45 and 46. The gas pressure within housing 40 is then increased to a high pressure through fitting 45 and the volume communicating therewith and at a low pressure in the volume communicating with fitting 46. Preferably, the gas to be used will be SF When the contact 97 is closed, and in the position of FIG. 5, a barrier is formed across housing 40 consisting of insulator 86, cylinder 85, members 92 and 93, and contact 97, the end of which is sealed by sealing ring 99. Thus, when con tact 97 is closed, chamber 120 can be held at high pressure, while chamber 121 will be a low pressure. When contact 97 is moved to the right, as shown in FIG. 6, this seal is opened, and high-pressure gas can flow from chamber 120, through the center of contact 97, through tubes 100 and 101 and through spider 106 until the shutoff valve 103 closes.

Operation'of the movable elements of the circuit breaker of the invention is obtained by applying highor low-control pressures to the various surfaces of contact 97 and cutoff valve 103. Thus, two conduits 122 and 123 each are controllably connected to either high or low pressure. Conduit 122 communicates with chamber 127 in front of contact 97, and with chamber 125 in front of valve 103. Conduit 123 communicates with chamber 124 behind contact 97 and chamber 128 behind valve 103. Clearly, the application of high pressure to conduit 122 and low pressure to conduit 123 will cause movement of both contact 97 and valve 103 to the right and from the position of FIG. 5 to the position of F IG. 6. Application of high pressure to conduit 123 and low pressure to conduit 122 will cause the reverse movement of contact 97 and valve 103.

The operation of the apparatus shown in FIGS. 5 and 6 is as follows:

With the main contact closed, as shown in FIG. 5, there will be a current path from bus 55, member 66, cluster contact 74, movable contact 97, cluster contact 95, cylinder 85, cylinder 82 and bus 56. Seal 99 on movable contact 97 forms a pressure barrier such that volume 120 is at high pressure such as 250 p.s.i.g. of SF while volume 121 (and the interior of tubes 101, 100, and the interior of contact 97) are at low pressure such as 45 p.s.i.g. Clearly these pressures are illustrative, and will vary depending on the rating of the breaker.

If the interrupter is to be opened, suitable valves (not shown) connect high pressure to conduit 122 and low pressure to conduit 123 such as 250 p.s.i.g. and 45 p.s.i.g., respectively.

These pressures may be derived from valving internal of the tank 40, with the high pressure derived from volume 120 and the low pressure derived from volume 121.

The application of high-control pressures to volumes 127 and 125 from conduit 122 forces contact 97 and valve 103 to the right. Contact 97 moves first since the ball mechanism 112 delays the movement of valve 103. The initial movement of contact 97 to the right opens the pressure seal so that high pressure is immediately applied over the full cross section of the left end of contact 97 thereby to apply high-accelerating force to open contact 97.

As contact 97 moves to the right, semistationary contact 72 maintains engagement therewith until the outer peripheral main contact surface of contact 97 leaves contact 74. The arcing contacts of contacts 72 and 97 then part, drawing an arc. At the same time, a blast of SF has been established through the annular area defined by the opened seal 99, with this gas passing through the arc to assist in extinguishing the arc. The gas path is controlled by the nozzle-shaped interior a of tube 100, and the arc subsequently transfers between arcing tips 71 and 114 where it is ultimately extinguished by the gas blast.

Note that the gas blast proceeds through tubes 100 and 101, and through the spider plate 106 and cylinder 112. Cylinder 112 may be of any desired material and is used to direct the hot gases away from the tank walls. If desired, an annular filter of a metal sponge, not shown, can surround the exterior of tube 112 to clean and cool the gas before it is returned to the compressor through fitting 46.

Once contact 97 has opened, valve 103 begins to move to the right and seals against annular seal 104. This cuts off the flow of high-pressure air from volume to volume 121, and the interrupter is now open. Note that the contact-open gap is immersed in high pressure, since high pressure from volume 120 extends into tubes 100 and 101 to seal 104.

In order to close the interrupter (from the position of FIG. 6 to the position of FIG. 5), high pressure is applied to conduit 123 and low pressure is applied to conduit 122. The high pressure in volumes 124 and 128 drives contact 97 and valve 103 to the left. The opening of valve 103 permits a blast of gas through the closing contacts to cool prearcing between the arcing tips of contacts 97 and 72 as they approach one another. After contacts 97 and 72 engage, they continue to move to the left until contact 97 is firmly seated within contact cluster 74 and valve 99 seats against plate 75 to cut off gas flow from volume 120 to volume 121.

FIGS. 7 and 8 show a second embodiment of the invention which incorporates changes essentially in the bus connections, control pressure input, and in the union between the movable contact and cutoff valve. FIG. 7 shows the device in the closed position above the centerline of the movable contact and in the open position below the centerline of the movable contact. In FIGS. 7 and 8, components similar to those of FIGS. 1 to 6 have similar identifying numerals.

Cylinder 41 and 42 of FIGS. 6 and 7 are of epoxy, and the end cups 43 and 44 are of steel and may have any desired length to obtain any desired tank volume. The exterior of cylinders 41 and 42 may be coated with a metallic paint so that the tank may be grounded. The body, however, is of insulation material to assist in distributing electrostatic stress and to prevent eddy currents in the cylinder wall. However, a conductive tank may be used and will have the advantage of centralizing the arc to reduce the loop effect created in the circuit breaker structure. Each of cylinders 49 and 42 have bosses 150 and 151 secured thereto which receive epoxy tubes 152 and 153 which receive buses 55 and 56 which have modified insulation coatings 154 and 155. Flanges 156 and 157 are threaded onto tubes 152 and 153, respectively, with buses 55 and 56 held in place by flanges 158 and 159, respectively. Buses 55 and 56 carry end plates 160 and 161 which receive mounting straps 162 and 163, respectively.

The stationary contact assembly 164 is mounted in part on strap 162 and consists of an outer cylinder 165 and inner contact body 166 having arcing contact tip 167 on the right-hand end thereof. Clamping plate 167a holds contact cluster 74 on the end of cylinder 165. Note that clamping plate 167a has a chamfered inner diameter to serve as a blast valve seal. A semistationary contact 168 having a biasing spring 169 is mounted between members 165 and 166. Members 165 and 166 are held in place by end plate 170. End plate 170 has a plurality of tie rods connected thereto, one of which is shown as insulation rod 171 within insulation cylinder 172. One end of rod 171 and cylinder 172 is connected to plate 170 and the other end thereof is fixed to insulation ring 173. Ring 173 is similar to ring 86 of FIG. 5, but has an extending portion 174 containing control pressure conduits 175 and 176.

Mounting strap 163, in part, carries the movable contact assembly and is secured to the opposite sides of exhaust tube 177 which extends from conductive cylinder 178. The lefthand end of cylinder 178 is fixed to plate 179 which receives contact cluster 95. A second clamping plate 179a is bolted to plate 179 and cylinder 178. A spider plate 180 and integral shutoff valve retainer body 181 are secured to cylinder 177 and a shutoff valve seal 182 is carried on body 181. A shockabsorbing dash pot 183 having an extending shaft 184 is mounted on body 181.

A single movable body 185 then forms the movable contact, cutoff valve, nozzle, and movable arcing contact. Thus, cylindrical movable contact 186 has blast valve seal 187 therearound and has a nozzle orifice 188 directly secured to its interior. The rear of contact 186 has a cutoff valve section 189 connected thereto which has an extending cylinder portion 190 forming a portion of a cutoff valve extending therefrom which can engage seal 182. An outwardly extending flange 191 then defines two control volumes 192 and 193 which communicate with control conduits 175 and 176, respectively. The arcing tip 190a is carried on shaft 191 which is connected to movable contact 186 by a suitable spider. This construction in which the buses 55 and 56 are easily disconnected from the circuit interrupter permits construction and test of the interrupter outside of the tank, and before the interrupter is inserted and sealed within the tank.

It will be seen that the operation of the device of FIGS. 7 and 8 is similar to that of FIGS. 5 and 6 where the application of high pressure to conduit 175 and thus region 192 and low pressure to conduit 176 and thus region 193 moves the movable contact to its open position (and the cutoff valve 190 to a closed position). Similarly, application of pressures in a reverse manner will move the movable structure to the left to close the main contacts. Note that while opening the interrupter, gas blast continues while the valve 190 is in transit to the valve-closed position. Dash pot 183 provides additional delay in closing valve 190. Moreover, the arc to contact tip 190a is constantly elongated, since tip 190 moves with contact 186 during circuit interruption.

FIG. 9 shows a modification of the stationary contact structure in which the semistationary contact 168 of FIG. 7 is eliminated. Thus, in FIG. 9, cylinder 165 of F IG. 7 is replaced by cylinder 200 while body 166 of FIG. 7 is replaced by body 201 which is connected to cylinder 200 through split contact cylinder 202 and bolt 203. Contact cylinder 202 has a plurality of contact fingers, such as fingers 204 and 205, extending therefrom which encircle, and are supported against the interior surface of cylinder 200. The fingers, such as fingers 204 and 205, extend beyond the right-hand end of cylinder 200 and each receive an inward bias from respective biasing springs, such as springs 206 and 207 for fingers 204 and 205, respectively, which springs are suitably secured to the end of cylinder 200. A corona shield and gas guide 208 surrounds the end of the stationary contact.

The spring fingers, such as fingers 204 and 205, engage the outer surface of movable contact 186. Arcing contact fingers, such as split contact fingers 209 and 210, encircle arcing contact rod 211 and are secured in the center of the end of body 201. A rubber disk 212 surrounds rod 211 and biases fingers 209 and 210 outwardly and into sliding contact with the inner diameter of contact 186. Contact fingers 209 and 210 and the interior of contact 186 have engaging surfaces formed of are resistant material. The contacttsurfaces of contacts 204, 205, 209 and 210, and the end of contact 186 are contoured such that the outer surface of contact 186 disengages contacts 204 and 205 before the inner surface of contact 186 disengages contacts 209 and 210. Thus, arcing duty on the contacts will be to arcing contacts 209 and 210, while main contact fingers 204 and 205 remain clean and unpitted.

The main pressure seal is then formed by sealing ring 213 which receives the annular end of contact 186 in sealing relation when the contacts are closed. Obviously, the interrupter operates as described for either FIGS. 5 and 6 or 7 and 8 when the stationary contact is modified as shown in FIG. 9.

FIG. 10 shows a modification of the arrangement of FIGS. 7 and 8 wherein the movable contact and valve are separated as in FIGS. 1 to 6 with a fixed arc contact spacing. In FIG. 10, components identical to those of FIGS. 7 and 8 have similar identifying numerals.

In FIG. 10, the movable contact assembly support cylinder 178 of FIG. 7 is modified as shown by cylinder 220 and carries a central conductive body 221 by a suitable internal spider arrangement. Body 221 carries a fixed arcing contact 222 having an arcing tip 223 and has a rear body portion 224 which communicates with discharge tube 225. The movable contact 186 of FIG. 7 is also modified in FIG. 10 to carry a cutoff valve seal 226 which faces away from and is shielded from the arc gases. A differential cutoff valve cylinder 227, having shoulder 228, is then mounted on body 221 and is biased to the left by spring 229. Conduit 176 is connected to enclosed annular volume 230 by channels 231, 232, 233 and 234. Cutoff valve is movable toward sealing engagement with seal 226, as shown below the centerline of contact 186.

In operation, high pressure applied to conduit 176 and low pressure applied to conduit closes contact 186 and holds valve 227 open against the force of spring 229. To open the interrupter, low pressure is applied to conduit 176 and high pressure is applied to conduit 175. This causes opening of contact 186, as described previously in FIG. 7, and permits closing of valve 227. Channel 234 can have a diameter sized to provide any desired time delay for the exhaust of high pressure from volume 230, thereby to delay the closing of valve 227 until the arc in the fixed gap between arcing electrodes 167 and 223 is extinguished. Note that hot arc gases will not strike the shielded cutoff valve seal 226.

FIGS. 11 and 12 show a further modification of the invention in which the movable contact, stationary contact and movable valve structure are altered as compared to the embodiments shown in FIGS. 5 to 10. Again, components similar to those of FIGS. 1 to 10 have similar identifying numerals.

The stationary contact structure 164 resembles that of FIG. 9, but is modified to obtain better arc control, as will be described. Contact structure 164 is supported by strap 162 and insulation rod and cylinder 171-172 which is attached between insulator 174 and plate 240. A conductive cylinder 241 carries segmented contact 242, having contact fingers including fingers 243 and 244 which are outwardly biased by spring biases 245 and 246. A clamping bolt 247 holds contact 242 in position. Each of the contact fingers 243 and 244 is terminated by arcing tips 248 and 249, respectively. The blast valve seal 250 is carried in the end of cylinder 241 and contact cluster 74 is sealed against the end of cylinder 241 by clamping plate 251.

Movable contact 255 in FIG. 11 consists of an elongated cylinder portion 256 which reaches seal 250 and is in sliding contact with both contact 74 and contact 95, and a body portion 257 which is secured to cylinder 256. Body portion 257 has an annular arcing contact portion 258 which also defines a gas nozzle (in the fashion of nozzle 188 of FIG. 7), and which engages the outer surface of and said hollow contact fingers 248 and 249. A flange 259 on body 255 defines two chambers 260 and 261 which are connected to control pressure conduits 262 and 263, respectively.

The stationary contact support cylinder is formed in two parts, 264 and 265, where section 264 receives plate 266 which carries contact 95 and clamping plate 267. Support part 265 carries body 268 and the arcing contact rod 269. A plurality of channels 270, 271 and 272 are formed in body 265, and a flange 271a of body 265 carries a cutoff valve seal 272a. Note that seal 272 is now stationary and is removed from the movable contact, as shown in FIG. 10. A movable cylindrical cutoff valve 273, biased to the left by spring 274 is then mounted between bodies 268 and 265. Valve 273 is controlled by pressure from conduit 263 which is connected to chamber 275 through conduit 276.

The operation of the device of FIGS. 11 and 12 is similar to that of the foregoing embodiment where application of suitable control pressure to conduits 262 and 263 control the movement of contact 255 and valve 273. The structure of FIGS. 11 and 12 has many advantages regarding ease of manufacture, but also has numerous advantages in the interruption of an arc. In particular, the use of the elongated contact section 256 permits an increase in area of the annular passage for flow of high-pressure gas when seal 250-256 is opened. Moreover, the arcing contact fingers 243 and 244 are buried" further down in the nozzle to improve arc interruption action and improved transfer of arc current to arcing rod 269. That is, the current path from contacts 248 and 249 to contact 258 is bent to define a blowoff which tends to move the arc inwardly and toward probe 269. In addition, valve seal 250 is out of the stream of arcing products.

In the embodiment of FIGS. 11 and 12, valve 273 is biased to the left by spring 274. If desired, spring 274 could be replaced by a suitable pneumatic biasing force derived from channel 262.

FIGS. 13, 14 and 15 show the manner in which three interrupters of the type shown in the foregoing figures can be mounted in three-phase relation in a switch gear frame. The switch gear of FIGS. 13, 14 and 15 forms an upper instrument compartment 290 (FIGS. 14 and 15), a circuit breaker compartment 291, a bus compartment 292 (FIG. 15) and a cable compartment 293.

Circuit breaker compartment 291 receives wheeled frame 294 which carries three interrupter assemblies 295, 296 and 297, each of which are identical to one of the devices previously described. Compressors 298, 299 and 300 are provided for each of interrupters 295, 296 and 297, respectively. Each of compressors 295, 296 and 297 are connected to suitable gas dryer and filter units 301, 302 and 303, respectively, which are of standard variety for the drying and filtering of SF,,. The high-pressure output of the compressors are connected to the high-pressure chamber of interrupters 298, 299 and 300 (for example, to fitting 45 of FIG. 1), while their lowpressure sides are connected, through dryer and filter units 301, 302 and 303, respectively, to the lowpressure chamber of interrupters 298, 299 and 300 (for example, to fitting 46 of FIG. 1). Control valves 304, 305 and 306 are provided for each of interrupters 295, 296 and 297, respectively, to control operating pressures applied, for example, to control conduits 122 and 123 of FIG. 1. This entire assembly, mounted on frame 294, may be rocked in and out of compartment 291.

The two buses of each of interrupters 295, 296 and 297 then are terminated with suitable disconnect contacts in the usual manner and have one terminal engageable with contacts con- Each of buses 307 and 312 extend through suitable current transformers mounted within bus compartment 292, shown, for example, by current transformers 313, 314 and 315 in FIG. 13.

Although this invention has been described with respect to particular embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and, therefore, the scope of this invention is limited not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A gas blast circuit interrupter comprising, in combination:

a. an elongated hollow housing;

b. a stationary contact support connected to said housing;

c. a movable contact support connected to said housing;

d. a stationary contact assembly connected to said stationary contact support and positioned generally on the axis of said hollow housing;

e. a movable contact assembly connected to said movable contact support and positioned generally on the axis of said hollow housing; said movable contact assembly including a hollow movable contact axially movable into and out of engagement with said stationary contact assembly;

1. an annular blast valve seal ring connected to said stationary contact assembly positioned coaxially with said hollow movable contact;

g. an elongated hollow sleeve extending from the end of said hollow movable contact movable into and out of sealing engagement with said blast valve seal ring and defining a movable blast valve seal ring;

h. gas barrier means extending in a plane from the interior surface of said hollow housing to the exterior surface of said movable contact assembly to define first and second pressure chambers within said hollow housing which are in communication with one another only through said movable and fixed blast valve seal rings when said seal rings are open by being spaced from one another; the region of engagement between said stationary contact assembly and said hollow movable contact and the region of engagement of said blast valve seal rings disposed in said first pressure chamber; said second pressure chamber having a volume equal to or greater than the volume of said first chamber; each of said first and second pressure chambers being isolated from the external atmosphere;

i. means for applying a gas at high pressure to said first pressure chamber and for applying a gas at a relatively lower pressure to said second pressure chamber;

j. a downstream cutoff valve connected to said movable contact assembly and in communication with the interior of said hollow movable contact; said downstream cutoff valve comprising a hollow sleeve disposed coaxially with said movable contact; said downstream cutoff valve operable between a valve-open and valve-closed condition for respectively permitting and preventing flow of gas from said first pressure chamber to said second pressure chamber when said movable and fixed blast valve seal rings are open;

k. operating means connected to said hollow movable contact and said cutoff valve for moving said hollow movable contact into and out of engagement with said stationary contact assembly, and for operating said downstream cu toff valve between its said valve-open and valve-closed conditions; said downstream cutoff valve in its said valveopen condition when said hollow movable contact engages said stationary contact assembly; said downstream valve being moved to said valve-open condition, and subsequently to said valve-closed condition when said hollow movable contact moves out of engagement with said stationary contact assembly;

I. recirculating pump means for pumping gas from said first pressure chamber to said second pressure-chamber to I restore the pressure differential therebetween to a given value;

in. and annular contact means connected to said hollow sleeve extending from said hollow movable contact for engaging the outer periphery of said hollow sleeve when said stationary contact engages said movable contact;

n. said stationary contact assembly including a hollow conductive tube extending coaxially with said hollow movable contact and having an outer diameter smaller than the inner diameter of said annular blast valve seal ring; said hollow movable contact having an inwardly restricted continuous diameter portion at the end thereof adjacent said stationary contact to define a gas blast nozzle; the interior diameter of said inwardly restricted diameter portion engaging the outer diameter of said extending hollow conductive tube when said stationary contact engages said movable contact;

0. said downstream cutoff valve comprising a hollow movable sleeve and an annular valve seat; said annular valve seat and hollow movable sleeve being coaxial with one another and with said hollow movable contact; said annular valve seat positioned between said stationary contact assembly and said hollow movable sleeve whereby said annular valve seat is shielded from are products createdfur hexafluoride.

3. The circuit interrupter of claim 1 wherein said operating means consists of a pneumatic operating structure including means for applying differential pressures in an axial direction to said hollow movable contact and said cutoff valve. 

1. A gas blast circuit interrupter comprising, in combination: a. an elongated hollow housing; b. a stationary contact support connected to said housing; c. a movable contact support connected to said housing; d. a stationary contact assembly connected to said stationary contact support and positioned generally on the axis of said hollow housing; e. a movable contact assembly connected to said movable contact support and positioned generally on the axis of said hollow housing; said movable contact assembly including a hollow movable contact axially movable into and out of engagement with said stationary contact assembly; f. an annular blast valve seal ring connected to said stationary contact assembly positioned coaxially with said hollow movable contact; g. an elongated hollow sleeve extending from the end of said hollow movable contact movable into and out of sealing engagement with said blast valve seal ring and defining a movable blast valve seal ring; h. gas barrier means extending in a plane from the interior surface of said hollow housing to the exterior surface of said movable contact assembly to define first and second pressure chambers within said hollow housing which are in communication with one another only through said movable and fixed blast valve seal rings when said seal rings are open by being spaced from one another; the region of engagement between said stationary contact assembly and said hollow movable contact and the region of engagement of said blast valve seal rings disposed in said first pressure chamber; said second pressure chamber having a volume equal to or greater than the volume of said first chamber; each of said first and second pressure chambers being isolated from the external atmosphere; i. means for applying a gas at high pressure to said first pressure chamber and for applying a gas at a relatively lower pressure to said second pressure chamber; j. a downstream cutoff valve connected to said movable contact assembly and in communication with the interior of said hollow movable contact; said downstream cutoff valve comprising a hollow sleeve disposed coaxially with said movable contact; said downstream cutoff valve operable between a valve-open and valve-closed condition for respectively permitting and preventing flow of gas from said first pressure chamber to said second pressure chamber when said movable and fixed blast valve seal rings are open; k. operating means connected to said hollow movable contact and said cutoff valve for moving said hollow movable contact into and out of engagement with said stationary contact assembly, and for operating said downstream cutoff valve between its said valve-open and valve-closed conditions; said downstream cutoff valve in its said valve-open condition when said hollow movable contact engages said stationary contact assembly; said downstream valve being moved to said valve-open condition, and subsequently to said valve-closed condition when said hollow movable contact moves out of engagement with said stationary contact assembly; l. recirculating pump means for pumping gas from said first pressure chamber to said second pressure chamber to restore the pressure differential therebetween to a given value; m. and annular contact means connected to said hollow sleeve extending from said hollow movable contact for engaging the outer periphery of said hollow sleeve when said stationary contact engages said movable contact; n. said stationary contact assembly including a hollow conductive tube extending coaxially with said hollow movable contact and having an outer diameter smaller than the inner diameter of said annular blast valve seal ring; said hollow movable contact having an inwardly restricted continuous diameter portion at the end thereof adjacent said stationary contact to define a gas blast nozzle; the interior diameter of said inwardly restricted diameter portion engaging the outer diameter of said extending hollow conductive tube when said stationary contact engages said movable contact; o. said downstream cutoff valve comprising a hollow movable sleeve and an annular valve seat; said annular valve seat and hollow movable sleeve being coaxial with one another and with said hollow movable contact; said annular valve seat positioned between said stationary contact assembly and said hollow movable sleeve whereby said annular valve seat is shielded from arc products created during arcing between said stationary and movable contacts; means for axially slidably mounting said hollow movable sleeve; and means for biasing said hollow movable sleeve toward engagement with said annular valve seat.
 2. The circuit interrupter of claim 1 wherein said gas is sulfur hexafluoride.
 3. The circuit interrupter of claim 1 wherein said operating means consists of a pneumatic operating structure including means for applying differential pressures in an axial direction to said hollow movable contact and said cutoff valve. 